[llvm] [InstSimplify] Fold value-preserving zext/sext of trunc (PR #204089)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

Looks like auto-merge was blocked.

> What do you think about adding a @llvm.assume to keep the information?

It is generally impossible. We cannot lift a deferred UB into an immediate UB.


https://github.com/llvm/llvm-project/pull/204089